Fingerprints and the Fundamentals of Evidence
The following are examples of what kind of evidence? Blood type, shoe prints, hair, and soil samples.
Identified (class) evidence
MISSION 4: FIBRE SORTING
Sort the following fibres (trace) into their respective categories. Synthetic or Natural, and then Animal and Plant.
Synthetic: Rayon, Teflon, Modal, Kevlar, Acetate, Viscose, Nylon
Natural:
Animal: Silk, Cashmere, Angora
Plant: Cotton, Linen, Coir, Ramie
What are the three primary types of agglutinogens discovered on the surface of red blood cells? What do they determine?
A, B, and Rh factor. They determine blood type, which can create identified (class) evidence.
Can a breathalyzer device be deceived? Name 2 possibilities of a breathalyzer providing false readings
Answers vary. A breathalyzer can not be deceived, but there are chances of inaccurate readings.
A person can be wrongfully given positive readings if they used breath fresheners (mouthwash) containing alcohol. Skewed readings can come from breathalysers having bad batteries or improper calibration.
What are the two things that the technique of forensic writing analysis is used to determine?
If a document was deliberately forged and find who is responsible for the criminal notes and documents.
Name the 2 components of lifting powders.
Pigment and binder (carriers)
What are the 2 main sources/types of trace evidence, and what are the differences?
Inorganic/Synthetic and Organic.
Inorganic: A substance with no carbon.
Organic: Substance with carbon
MISSION 3: BLOOD SPATTER ANALYSIS
Ava Tasse was murdered at her bakery an hour after they closed. Analyze the blood spatter diagrams to create a rough hypothesis of the events on the night of the murder. Observe spatter lengths, spacing, and shape to figure out the movements of the killer and possible causes of death.
What happens to a person who refuses a breathalyzer test?
If a suspect refuses a breathlyzer, they are charged with “refusal to provide a breath sample,” which is an offense with the same penalty as impaired driving.
What is thin-layer chromatography, and why is it used?
Answers vary; a summarized, less in-depth version of this is fine. Ink is added to an absorbent material, like paper. The molecules making the ink are absorbed into the paper. Small amounts of either ethanol or acetone are placed in the beaker to slowly travel up the paper. The movement separates the components of the ink into certain points along the paper. A chromatographic pattern is created, with unique components used to trace the type of pen used in a note, providing identified (class) evidence.
A murderer is running away from the police. They climb up a freshly painted fence while running away and escape the crime scene. The next morning, investigators see the killer's fingerprints dried onto the fence. What type of fingerprint is this?
Physical/molded fingerprint
What was Locard’s exchange principle, and how did it cause a breakthrough in forensic science?
Locard’s exchange principle stated that whenever two things came in contact with each other, there was some kind of exchange between them. So, if a sugar cube and a pile of sand were to touch, traces of sugar would be found in the sand, and sand would be found on the sugar cube. This became the basis of forensic science. Locard’s principle proved to be effective and applicable in most physical crime cases. It most specifically made a breakthrough in the world of trace evidence.
The Kastle-Meyer, Leucocrystal Violet, and Luminol tests are all what type of tests?
They are presumptive tests that are used (first) to indicate the presence of a substance (blood, bleach, and bodily fluids).
Which part of the brain is most sensitive to BAC?
The cerebrum.
MISSION 1: HANDWRITING ANALYSIS
When collecting evidence at the scene of a murder, you spot a small paper covered in blood. The murderer wrote you and your fellow detectives a note. The note reveals that the crime is linked to a series of prior homicides around the city. You call some suspects in to write a sample sentence to compare the notes. Can you identify the killer?
The murderer is suspect 2.
What are cyanoacrylate fuming and iodine fumigation used for? Name 2 major differences. (Like what they are used for, components, etc.)
Part 1: These chemicals react with oils left behind by fingerprints to create a visible image. They are used with materials like paper or wool that absorb the oil, making traditional lifting impossible.
Part 2: Answers vary.
Iodine Fuming: The iodine sublimes (is heated up and turns from a solid directly to a gas state) and reacts with the lipid components of the oils left behind in fingerprints. Used on low-density and lightweight objects. Prints fade, so a fixing solution must be added to the print.
Cyanoacrylate: Uses cyanoacrylate, which is the main component of Super Glue. The cyanoacrylate is heated in a chamber and turns to vapor. When it reacts to the fingerprint oil, it produces a whitish grey film.
Name the four steps of collecting trace evidence. For 100 bonus points, explain the chain of custody.
Step 1: Securing the crime scene to ensure everyone involved is safe. (Questioning. This helps law enforcement identify key witnesses/suspects.)
Step 2: Observations of the crime scene. (Before evidence is actually collected, the unaltered state of the crime scene is photographed and altered.)
Step 3: Collection of trace evidence.
Step 4: Packaging and Preservation. (Trace evidence is labeled with date, time, case number, and a brief description. Evidence is double-packaged and stored in evidence drawers.)
Chain of Custody: After the evidence is packaged and preserved, strict records must be kept of who has had access to the evidence.
You cut your finger, and a drop falls onto the counter. What would happen to the next droplet if you lifted your finger one foot, and which part of the spatter will dry first?
The droplet will increase in diameter. The outer edges of the spatter will dry first.
MISSION 5: ALCOHOL BEVERAGES
Match types of alcoholic drinks with their ABV and characteristics. You catch an intoxicated driver on the road, which drink would a person need less of, or more of, to be impaired?
A can of beer: ABV: 5% alcohol. The most popular alcoholic beverage globally.
A glass of table wine: ABV: 12% alcohol. The most ancient and diverse alcoholic beverage.
A glass of malt liquor: ABV: 7% alcohol. Originated in Europe, popularized by America in the ‘30s and ‘40s
A shot of vodka: ABV: 40% alcohol. Not gluten-friendly, as it is fermented with ingredients such as barley, potatoes, rye, and wheat.
Pure Alcohol: ABV: 100% alcohol. Not safe for consumption.
What are the three basic types of questioning techniques used by polygraph examiners? Give a scenario including at least one.
Relevant/Irrelevant technique, control question technique, and concealed information technique.
Mission 2: Fingerprint Identification
There was a fatal stabbing in your town. Two people were killed, and the murderer escaped from the scene. You were called to analyze and compare fingerprints to find the potential murderer. Patent fingerprints (prints left in the dry blood) were collected, and one latent print was lifted from the scene. Compare the partial prints collected to the prints collected and identify our killer! *This is a harder one; more time can be given.*
The murderer is Suspect 1.
Name 2 main microscopic differences between human and animal hair.
Answers vary.
Human hair: Has uniform coloring throughout. It is darker near the cuticle. Amorphous Medulla.
Animal Hair: Color found in bands, randomly through the hair. Daker near the medulla. Regularly structured medulla
What percentage of people in North America are secretors? Name 3 things that are present in a secretor’s blood and also other bodily fluids.
Around 80% of North Americans are secretors. Answers vary. Antigens, antibodies, proteins, and enzymes.
Prior to the breathalyzer test, the drunkometer was used. Explain how it worked and why it is no longer used today.
Answers vary.
How it worked: An individual blew into a breath test bag. The alcohol in their breath reacts to become acetic acid which changes the color of the solution in the bag. The more acetic acid, the more of a color change.
Problems with the device: The results were only qualitative (dependent on the color change). A device with quantitative results was needed. It also needed to be re-calibrated after every use which was inconvenient and time consuming.
In 1987, following the results of the R.v. Beland case, what did the Supreme Court state/decide about the use of polygraph evidence in court?
They stated that polygraph evidence was inadmissible in court due to the opinion that it “unnecessarily complicates the process and brings in too much uncertainty and possibility for error.” Also, because of polygraph deception and inaccuracy, which creates doubt about its validity.